Various kinds of devices comprise a user interface that is touch-sensitive. Touch sensitive panels and screens allow a user to interact with the device by touching e.g. pictures, words, symbols or buttons on a touch sensitive surface. Touch sensitive technology can be used as an alternative user interface with applications that normally use electromechanical keyboards or buttons. Some computer applications are designed specifically for touch sensitive technology, often having larger icons and links than a typical, e.g. PC application. The following lists typical types of touch screen technology:                Resistive: A resistive touch screen panel is coated with a thin metallic electrically conductive and resistive layer that causes a change in the electrical current which is registered as a touch event and sent to the controller for processing.        Surface wave: Surface wave technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing.        Capacitive: A capacitive touch screen panel is coated with a material that stores electrical charges. When the panel is touched, a small amount of charge is drawn to the point of contact. Circuits located at each corner of the panel measure the charge and send the information to the controller for processing. Capacitive touch screen panels must be touched with a finger unlike resistive and surface wave panels that can use fingers and stylus.        
For example, Personal Digital Assistants (PDA) typically comprise a large display area in proportion to the size of the device. Most PDAs include only a few mechanical buttons in order to provide as large display area as possible. Therefore, the display area is also used as an input device. The display area is usually touch-sensitive so that information can be transferred into the device just by touching the display or using a special tool, e.g. a special pen (i.e. stylus).
A touch screen may also be a touch-sensitive panel. U.S. Pat. No. 5,241,308 (Paragon Systems) describes a touch-sensitive panel for generating selected ones of any of a plurality of different signals, each of which is generated by touching a different location on the panel. The apparatus includes also force-sensing means for sensing the magnitudes of the forces that are applied to each panel member support by the panel member when the member is touched at a selected location.
Let's assume that a hand-held device has a display that is covered by a lens (touch sensitive panel). One or more force sensors are attached to the lens in order to determine the point of application on the lens. Each of the force sensors produces a signal in response to a touch on the lens. The signals are received and processed with a processing unit. When the device is kept e.g. in hand and the hand moves, the movement itself produces signals that are not a result of a touch on the lens. If the lens is touched at the same time as the hand moves, the signals comprise two separate signal components: a signal component produced by the touch and a signal component produced by the hand movement. In practice, the signal component produced by the movement is an interference signal that distorts the actual touch signal component. Due to the distortion, the actual point of touch may be determined erroneously.
The same problem applies also to e.g. a situation in which a device having a touch panel (or equivalent) is arranged to be used in a vehicle. Vibrations of the vehicle and variations in acceleration of the vehicle induce interference signal components to the signals of the force sensors.
Based on the above there is an obvious need for a solution that would mitigate and/or alleviate the above drawbacks.